Implantable sensors, such as optical, chemical or biochemical sensors, are known which can be implanted within a living animal and which measure the presence or concentration of an analyte or substance of interest in a medium within the living animal. Optical sensors may include one or more light sources, such as one or more LEDs, one or more photodetectors, such as one or more photodiodes, and a layer of indicator molecules that emit a detectable optical signal, e.g., fluoresce, when optically excited by the light source. The light source(s) emits an excitation light signal that impinges upon the indicator molecules, and the indicator molecules emit a signal (which can be a function of the presence and/or concentration of the analyte of interest if present), at least some of which impinges upon the photodetector(s), which convert the detected light into an electrical signal.
An exemplary sensor of this type is described in United States Patent Application Publication No. 2013/0211213, the disclosure of which is hereby incorporated by reference.
Current sensor configurations allow for light other than that emitted by the indicator molecules, such as ambient light, to impinge on the photodetector(s) from a variety of angles. This “stray” light impinging upon the photodetector(s) adds noise to the measurements. Current sensor configurations also tend to lose much of the desired excitation light to areas of the sensor which are not statistically relevant to light measurement calculation.
To subtract out the undesired stray light signals and reduce signal noise due to such stray light, current sensor configurations employ light filters and/or algorithm calculations to subtract out stray light noise and/or employ the location of the indicator molecules relative to the optics components to maximize incident excitation light and detected emission light while minimizing stray light signals.
It thus would be desirable to more effectively block the incidence of stray light signals onto the photodetectors of a sensor and to more effectively control the dispersal of the excitation light.